430
FXUS65 KCYS 010551
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1151 PM MDT Tue Apr 30 2024

.KEY MESSAGES...

- Strong winds likely with and behind the front across the
  Laramie Range Tuesday morning. Gusts up to 60 mph possible.

- A series of weather disturbances will move across the
  forecast area Thursday and Friday, producing a chance of
  showers and thunderstorms mainly during the afternoons and
  evenings.

- Drier and warmer conditions are anticipated for the weekend.

&&

.UPDATE...
Issued at 539 PM MDT Tue Apr 30 2024

Latest surface analysis was showing the surface low continuing
to push east across the northern Plains with weakening pressure
gradients starting to take place across the forecast area. Wind
speeds are still hanging around 50 mph around Bordeaux and Bear
Creek, but these wind speeds will continue to diminish fairly
quickly after sunset. As a result, we are going to let the High
Wind Warnings expire at 6pm.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 232 PM MDT Tue Apr 30 2024

Gusty afternoon winds have reached over 50 knots in several
locations across southeast Wyoming as well as even a few isolated
gusts over 50 knots in western Nebraska. As surface gradients relax
this evening, expect wind speeds to quickly drop back around 0z.
After sunset, most locations should be back below 30 mph save for
perhaps the elevated wind corridors along the Snowy Range Foothills.
Forecast guidance remains in tight agreement showing fast flow aloft
with relatively dry soundings in the lowest few km. Will favor a
partly to mostly cloudy overnight with seasonably mild temperatures
as our next system approaches from the west.

On Wednesday, a shortwave trough will dive through the northern
Rockies. This will turn flow aloft southwesterly through the day and
usher in elevated PWAT values in the form of mid and upper-level
moisture from the Pacific. A favorable zone of lift develops over
the northern Front Range and southern mountains by around 18z and
short-term forecast guidance has consistently depicted a period of
moderate snowfall in the Snowy and Sierra Madre ranges on Wednesday
afternoon. The period of snow should be fairly brief however, coming
to an end around 0z as the energy with this shortwave trough heads
east into the high plains. East of the I-25 corridor, surface flow
will turn to easterly upslope during the afternoon hours,
especially in the Nebraska Panhandle. Although moisture return
with this easterly flow looks rather paltry, some CAM guidance
does support surface dewpoints near or just above 40 degrees
from Sidney to Alliance after 21z. If sufficient low-level
moisture can advect northeastward in this return surface flow,
there may be just enough instability out there for a few
thunderstorms in the Cheyenne County through Morrill County
corridor capable of producing some sub-severe hail. Any activity
that does develop should quickly move east of the CWA by around
1-2z. Have increased PoPs in the Nebraska Panhandle as well as
the probability of thunder to cover this threat. Overall, expect
a drying and clearing trend overnight on Wednesday night with
temperatures running much colder than on Tuesday night in the
wake of the front.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 232 PM MDT Tue Apr 30 2024

Shortwave city in the long term as an active synoptic pattern leads
to mostly unsettled weather into next week.

Shortwave one of the long term arrives Thursday, bringing with it
cooler temperatures. 700 mb temperatures will be on the chilly side,
falling below 0C behind the FROPA. This will lead to high
temperatures below average for the beginning of May! Highs will be
in the 40s west of the Laramie Range and predominately 50s for the
eastern plains. Luckily, post-frontal, conditions look relatively
dry with minimal chances for precipitation during the day Thursday.
Shortwave two arrives Friday, bringing continued cold air and a
better chance for precipitation. Similar high temperatures are
expected Friday. This shortwave originates over the Pacific, so
there will be more moisture associated with it. Some jet energy
associated with this system will likely bring widespread light
precipitation to the CWA. Temperatures may be cold enough out
west to see snow, while the eastern plains should remain rain.
Non-zero CAPE values exist across the area so a brief
thunderstorm and/or a few rumbles of thunder will be possible.

A brief break from the shortwaves arrives just in time for the
weekend. A progressive upper-level ridge will move across the
Rockies and into the plains over the weekend. As a result, drier and
warmer weather is expected. Temperatures will warm on Saturday to
near-average, while temperatures on Sunday will further warm to
above average! Highs by Sunday could be in the 70s to low 80s in the
eastern plains!

The warmer and drier weather will be short-lived as another
potential system moves in during the beginning of the next work
week. However, models diverge on solutions, so will not go into
too much detail. But, it does look like it will at least be
cooler.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1146 PM MDT Tue Apr 30 2024

Southwest flow aloft will prevail, with a weather disturbance
moving across the terminals today producing some showers.

Wyoming TAFS...Ceilings will range from 5000 to 10000 feet with
showers in the vicinity of Laramie and Cheyenne from 08Z to 02Z.
Winds will gust to 25 knots at all terminals after 14Z.

Nebraska TAFS...Ceilings will vary from 4000 to 10000 feet with
occasional showers this morning through early evening reducing
visibilities to 5 miles at times. Winds will gust to 35 knots.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

UPDATE...REC
SHORT TERM...MAC
LONG TERM...SF
AVIATION...RUBIN